Relationship between clinicopathological characteristics and PET/CT uptake in lung cancer: [¹⁸F]FAPI versus [¹⁸F]FDG

This study aimed to characterize the relationships between parameters of [¹⁸F]fibroblast activation protein inhibitor (FAPI) and [¹⁸F]fluorodeoxyglucose (FDG) uptake in primary lung cancer lesions on positron emission tomography/computed tomography (PET/CT) and the clinicopathological features of lung cancer patients.

In this secondary analysis of a prospective trial, from December 2020 to January 2022, 62 patients with pathologically confirmed lung cancer were recruited continuously at a single center, and matched [¹⁸F]FAPI and [¹⁸F]FDG PET/CT examinations were performed, within 7 days but at least 20 h apart.

Analysis of the paired [¹⁸F]FAPI and [¹⁸F]FDG PET/CT scanning results of 62 lung cancer patients showed significant differences in [¹⁸F]FAPI uptake among different clinical stages (maximum standardized uptake value [SUVmax], p = 0.017, peak standardized uptake value [SUVpeak], p = 0.018, tumor-to-background ratio [TBR], p = 0.015) and different histological types (SUVmax, p = 0.039, SUVpeak, p = 0.034, TBR, p = 0.012), but no corresponding differences in [¹⁸F]FDG uptake (all p > 0.05). Compared with patients with a programmed cell death ligand 1 (PD-L1) tumor proportion score (TPS) ≥ 1 %, patients with a TPS < 1 % had a higher FAPI-avid tumor volume (FTV) of [¹⁸F]FAPI (p = 0.041) and a higher metabolic tumor volume (MTV) of [¹⁸F]FDG (p = 0.029). Compared with patients with Ki-67 score < 50 %, patients with Ki-67 score ≥ 50 % had higher SUVmax, SUVpeak, and total lesion glycolysis (TLG) of [¹⁸F]FDG (p = 0.027, 0.025, and 0.021, respectively).

Our results indicate that [¹⁸F]FAPI and [¹⁸F]FDG uptake are related to different clinicopathological features of lung cancer, providing insights supporting a more comprehensive understanding of the characteristics of lung cancer.